Why do they dock (or cut)
The tails on brittany pups?

For show! Unless it is a show dog that has to meet certain criteria, the tail should be left intact. Even then I don't think it should be done. I think it's very cruel and doesn't serve any purpose whatsoever. Why put a dog through that pain unnecessarily?

Vet said he shoots them with pain killer and you do it so young it does not affect them
I have never seen a brit that I have hunted with have a long tail and none of them were show dogs

After all baby boys (most ) get circumcised

Most vets, where I live anyway, absolutely refuse to do it anymore. It's painful whether they are a puppy or not, and it's just not needed. It serves no purpose. It's a lot different than being circumsized. The tail is more than just skin.

Hello aros!

Do you have a dog whose tail has already been docked? Or are you in a position to decide whether your (practically newborn puppy, I hope) will be getting docked?

I was in the latter position this year. We were adopting our English cocker spaniel (it's a breed of dog that is traditionally docked), and as we were there on the day of his birth, we had the option of having his tail docked or left intact. After a lot of speedy but thorough research on the subject, we decided to let the puppy keep his lovely tail. And do you know what? I'm soooo happy with the decision. Every time I see it wagging, I have to smile.

There was another thread on tail docking not long ago, and you can find a ton of information there, including the historical reasons for tail docking and numerous arguments against the practice. I also posted there and included various links you can follow for more information.

This is the link:
https://www.askmehelpdesk.com/dogs/12-week-old-boxer-tail-docking-259038.html